Generic Routing Encapsulation (GRE)
- IP Protocol 47
- In the IP header there is a protocol field
- Tunnel interface
- If a router does IP and does GRE you can create a tunnel between two sites anywhere on the internet
- "The network duke tape"
- Point-to-point & multipoint support
- Supports non-IP traffic
- Wherever I go I can get internet access and as long as I have internet I can create a GRE tunnel
- No encryption and no authentication
- Weird scenarios where we have no IP traffic
- "User defined pipe" over IP
Generic Encapsulation
- "Just a box"
- Any payload
- Any destination
- No encryption
- Typically processed in software
- Software function that runs in your CPU
- Constantly interrupting the general purpose CPU to perform that function.
- Example:
- CPU - Generic
- GPU - Blazing fast
- ASIC - This is why switches are fast
- Impacts how that router is going to run